Problem: $ A = \left[\begin{array}{rr}3 & 9 \\ 9 & 4\end{array}\right]$ What is $ A^{T}$ ?
Answer: To find the transpose, swap the rows and columns. $ A^{T}$ = $\left[\begin{array}{rr}3 & 9 \\ 9 & 4\end{array}\right]$